GNAT.sockets UDP Example

GNAT.sockets UDP Example

[arvids lemchens]

Hello,

i am looking for a very short and simple example how to send an
(empty) UDP-datagram with GNAT (3.14p, Linux).

Found one for TCP, but didn't get it to switch to UDP.

Somehow it seems that i am to simpleminded for the "Send_Socket".

MvfG,

Arvids

Re: GNAT.sockets UDP Example

[David C. Hoos, Sr.]

----- Original Message ----- 
From: "arvids lemchens" <lemchens@lemmies.lb.bawue.de>
Newsgroups: comp.lang.ada
To: <comp.lang.ada@ada.eu.org>
Sent: November 15, 2002 3:48 PM
Subject: GNAT.sockets UDP Example


> Hello,
> 
> i am looking for a very short and simple example how to send an
> (empty) UDP-datagram with GNAT (3.14p, Linux).
> 
> Found one for TCP, but didn't get it to switch to UDP.
> 
> Somehow it seems that i am to simpleminded for the "Send_Socket".
> 
It's hard to guess what you might be doing wrong, without your code.

One guess -- did you create your socket like this?
Create_Socket (Socket, Family_Inet, Socket_Datagram);

How do you know that you didn't send correctly?  Could the problem
be on the receiving end?

What platform/OS are you using?

I have used GNAT sockets for TCP, UDP (broadcast and point-to-point),
and multicast with great success, by none of my examples is short or
simple.

Re: GNAT.sockets UDP Example

[arvids lemchens]

Hello David,

david.c.hoos.sr@ada95.com am 16.11.02 um 05:27 in comp.lang.ada:
> ----- Original Message -----
> From: "arvids lemchens" <lemchens@lemmies.lb.bawue.de>
>> Found one for TCP, but didn't get it to switch to UDP.
>> Somehow it seems that i am to simpleminded for the "Send_Socket".
> It's hard to guess what you might be doing wrong, without your code.

Ok, stripped my code to the essentials:

-----
with GNAT.Sockets; use GNAT.Sockets;
with GNAT.Calendar.Time_IO; use GNAT.Calendar.Time_IO;
with Ada.Text_IO;
with Ada.Command_Line; use Ada.Command_Line;
with Ada.Exceptions; use Ada.Exceptions;
with Ada.Calendar; use Ada.Calendar;
with Interfaces; use Interfaces;
with Ada.Streams; use Ada.Streams;

procedure myrdate is
    Address  : Sock_Addr_Type;
    Socket   : Socket_Type;
    Channel  : Stream_Access;
    LTime    : Time;
    RTime    : Unsigned_32;
    SockRet  : Integer;
    Kahnung  : Ada.Streams.Stream_Element_Array := (1, 2, 3);

begin
    Initialize (Process_Blocking_IO => False);
    Address.Addr := Addresses (Get_Host_By_Name(Argument(1)), 1);
    Address.Port := 37;
    Create_Socket (Socket, Family_Inet, Socket_Datagram);
    --  Rest from TCP
    --    Connect_Socket (Socket, Address);
    --    Channel := Stream (Socket);
    Send_Socket (Socket, Kahnung, Kahnung(2));
    --  Here should come Receive_Socket
    LTime := Clock;
    RTime := Unsigned_32'Input (Channel);
    --  Here should come Bitmanipulation
    Close_Socket(Socket);
    Finalize;
end myrdate;
-----

If i try to compile it:

-----
ich@pc3:/transfer/ich2/ada/my/myrdate$ gnatmake -gnatf sendudp.adb
gnatgcc -c -gnatf sendudp.adb
sendudp.adb:10:11: warning: file name does not match unit name, should be "myrdate.adb"
sendudp.adb:27:05: no candidate interpretations match the actuals:
sendudp.adb:27:05: missing argument for parameter "To" in call to "send_socket" declared at g-socket.ads:653
sendudp.adb:27:35: expected type "Ada.Streams.Stream_Element_Offset"
sendudp.adb:27:35: found type "Ada.Streams.Stream_Element"
sendudp.adb:27:35:   ==> in call to "Send_Socket" at g-socket.ads:645
gnatmake: "sendudp.adb" compilation error
ich@pc3:/transfer/ich2/ada/my/myrdate$
-----

also tried different variants of the Send_Socket, but always there are
(different) errors.

Seems that i am missing some elementary knowledge about streams.

> One guess -- did you create your socket like this?
> Create_Socket (Socket, Family_Inet, Socket_Datagram);

That part is ok.

> How do you know that you didn't send correctly?  Could the problem
> be on the receiving end?

No, it even doesn't compile. The Network itself is fine.

> What platform/OS are you using?

Linux.

> I have used GNAT sockets for TCP, UDP (broadcast and point-to-point),
> and multicast with great success, by none of my examples is short or
> simple.

Confusing too, i found that there seems to be two different
Send_Socket's in GNAT-Sockets (using send and sendto).

How do i know which the Compiler will use?

Meanwhile i realized that also the Part with the Bitmanipulation is
too complicated, at least for my current level of knowledge.

So i am starting to think about some easier "Learning-by-doing"-
exercises for me and leave the rdate for later.

But if it is only a little modification do get above code running
i would be appreciate for seeing possibel corrections.

Thanks in advance.

MvfG,

Arvids

Re: GNAT.sockets UDP Example

[Simon Wright]

lemchens@lemmies.lb.bawue.de (arvids lemchens) writes:

> If i try to compile it:
> 
> -----
> ich@pc3:/transfer/ich2/ada/my/myrdate$ gnatmake -gnatf sendudp.adb
> gnatgcc -c -gnatf sendudp.adb
> sendudp.adb:10:11: warning: file name does not match unit name, should be "myrdate.adb"
> sendudp.adb:27:05: no candidate interpretations match the actuals:
> sendudp.adb:27:05: missing argument for parameter "To" in call to "send_socket" declared at g-socket.ads:653
> sendudp.adb:27:35: expected type "Ada.Streams.Stream_Element_Offset"

I don't know what you think this means -- if you look at the spec of
Send_Socket it says

   procedure Send_Socket
     (Socket : Socket_Type;
      Item   : Ada.Streams.Stream_Element_Array;
      Last   : out Ada.Streams.Stream_Element_Offset);
   --  Transmit a message to another socket. Note that Last is set to
   --  Item'First when socket has been closed by peer. This is not an
   --  error and no exception is raised. Raise Socket_Error on error;

Last is an *out* parameter, which means you need to supply an actual
variable of the correct type.

       Kahnung  : Ada.Streams.Stream_Element_Array := (1, 2, 3);
       Last : Ada.Streams.Stream_Element_Offset;

   begin
       Initialize (Process_Blocking_IO => False);
       Address.Addr := Addresses (Get_Host_By_Name(Argument(1)), 1);
       Address.Port := 37;
       Create_Socket (Socket, Family_Inet, Socket_Datagram);
       --  Rest from TCP
       --    Connect_Socket (Socket, Address);
       --    Channel := Stream (Socket);
       Send_Socket (Socket, Kahnung, Last);

> sendudp.adb:27:35: found type "Ada.Streams.Stream_Element"
> sendudp.adb:27:35:   ==> in call to "Send_Socket" at g-socket.ads:645
> gnatmake: "sendudp.adb" compilation error

When I correct this error I get (GCC-3.2, compiling with -bargs -E):

   smaug.pushface.org[15]$ ./myrdate myrouter

   Execution terminated by unhandled exception
   Exception name: GNAT.SOCKETS.SOCKET_ERROR
   Message: [107] Transport endpoint is not connected
   Call stack traceback locations:
   0x8062e3d 0x806350d 0x804a6d3 0x804a4f2 0x4003d27e

and I suspect maybe you need to call Bind_Socket??? -- hmm, now I get

   smaug.pushface.org[16]$ ./myrdate myrouter

   Execution terminated by unhandled exception
   Exception name: GNAT.SOCKETS.SOCKET_ERROR
   Message: [13] Permission denied

whereas

   Send_Socket (Socket, Kahnung, Last, Address);

ends up with a constraint error. Oh well, I guess I need to get GDB
working now ...

Re: GNAT.sockets UDP Example

[David C. Hoos, Sr.]

"arvids lemchens" <lemchens@lemmies.lb.bawue.de> wrote in message
news:8a2dx5TkACB@lemmies.lb.bawue.de...
> Hello David,
>
> david.c.hoos.sr@ada95.com am 16.11.02 um 05:27 in comp.lang.ada:
> > ----- Original Message -----
> > From: "arvids lemchens" <lemchens@lemmies.lb.bawue.de>
> >> Found one for TCP, but didn't get it to switch to UDP.
> >> Somehow it seems that i am to simpleminded for the "Send_Socket".
> > It's hard to guess what you might be doing wrong, without your code.
>
> Ok, stripped my code to the essentials:
>
> -----
> with GNAT.Sockets; use GNAT.Sockets;
> with GNAT.Calendar.Time_IO; use GNAT.Calendar.Time_IO;
> with Ada.Text_IO;
> with Ada.Command_Line; use Ada.Command_Line;
> with Ada.Exceptions; use Ada.Exceptions;
> with Ada.Calendar; use Ada.Calendar;
> with Interfaces; use Interfaces;
> with Ada.Streams; use Ada.Streams;
>
> procedure myrdate is
>     Address  : Sock_Addr_Type;
>     Socket   : Socket_Type;
>     Channel  : Stream_Access;
>     LTime    : Time;
>     RTime    : Unsigned_32;
>     SockRet  : Integer;
>     Kahnung  : Ada.Streams.Stream_Element_Array := (1, 2, 3);
>
> begin
>     Initialize (Process_Blocking_IO => False);
>     Address.Addr := Addresses (Get_Host_By_Name(Argument(1)), 1);
>     Address.Port := 37;
>     Create_Socket (Socket, Family_Inet, Socket_Datagram);
>     --  Rest from TCP
>     --    Connect_Socket (Socket, Address);
>     --    Channel := Stream (Socket);
>     Send_Socket (Socket, Kahnung, Kahnung(2));
The compiler messages mean exactly what they say.  You need to
read and understand them.

For a connectionless socket, you need the four-parameter version of
Send_Socket, otherwise the destination address is unspecified,
so you need

      Send_Socket (Socket, Kahnung, Last, Address);

where Last has been declared as:
    Last     : Ada.Streams.Stream_Element_Offset;

You really need to read and understand the GNAT>Sockets specification,
and the comments which accompany each item.

>     --  Here should come Receive_Socket
>     LTime := Clock;
>     RTime := Unsigned_32'Input (Channel);
>     --  Here should come Bitmanipulation
>     Close_Socket(Socket);
>     Finalize;
> end myrdate;
> -----
>
> If i try to compile it:
>
> -----
> ich@pc3:/transfer/ich2/ada/my/myrdate$ gnatmake -gnatf sendudp.adb
> gnatgcc -c -gnatf sendudp.adb
> sendudp.adb:10:11: warning: file name does not match unit name, should be "myrdate.adb"
> sendudp.adb:27:05: no candidate interpretations match the actuals:
> sendudp.adb:27:05: missing argument for parameter "To" in call to "send_socket" declared at
g-socket.ads:653
> sendudp.adb:27:35: expected type "Ada.Streams.Stream_Element_Offset"
> sendudp.adb:27:35: found type "Ada.Streams.Stream_Element"
> sendudp.adb:27:35:   ==> in call to "Send_Socket" at g-socket.ads:645
> gnatmake: "sendudp.adb" compilation error
> ich@pc3:/transfer/ich2/ada/my/myrdate$
> -----
>
> also tried different variants of the Send_Socket, but always there are
> (different) errors.
>
> Seems that i am missing some elementary knowledge about streams.
>
> > One guess -- did you create your socket like this?
> > Create_Socket (Socket, Family_Inet, Socket_Datagram);
>
> That part is ok.
>
> > How do you know that you didn't send correctly?  Could the problem
> > be on the receiving end?
>
> No, it even doesn't compile. The Network itself is fine.
>
> > What platform/OS are you using?
>
> Linux.
>
> > I have used GNAT sockets for TCP, UDP (broadcast and point-to-point),
> > and multicast with great success, by none of my examples is short or
> > simple.
>
> Confusing too, i found that there seems to be two different
> Send_Socket's in GNAT-Sockets (using send and sendto).
>
> How do i know which the Compiler will use?
>
> Meanwhile i realized that also the Part with the Bitmanipulation is
> too complicated, at least for my current level of knowledge.
>
> So i am starting to think about some easier "Learning-by-doing"-
> exercises for me and leave the rdate for later.
>
> But if it is only a little modification do get above code running
> i would be appreciate for seeing possibel corrections.
>
> Thanks in advance.
>
> MvfG,
>
> Arvids
>
> _______________________________________________
> comp.lang.ada mailing list
> comp.lang.ada@ada.eu.org
> http://ada.eu.org/mailman/listinfo/comp.lang.ada
>
>

Re: GNAT.sockets UDP Example

[arvids lemchens]

Hello David,

david.c.hoos.sr@ada95.com am 17.11.02 um 07:26 in comp.lang.ada:
> The compiler messages mean exactly what they say.  You need to
> read and understand them.

I know, i am still learning.

> For a connectionless socket, you need the four-parameter version of
> Send_Socket, otherwise the destination address is unspecified,
> so you need
>       Send_Socket (Socket, Kahnung, Last, Address);

That was my first attempt, later i switched to the three-parameter as
i get more and more confused about two different Send_Socket's in
GNAT.Sockets.

> where Last has been declared as:
>     Last     : Ada.Streams.Stream_Element_Offset;

Thanks, that helped.

Now it compiles and Datagrams work.


MvfG,

Arvids

Re: GNAT.sockets UDP Example

[arvids lemchens]

Hello Simon,

simon@pushface.org am 17.11.02 um 12:38 in comp.lang.ada:
> lemchens@lemmies.lb.bawue.de (arvids lemchens) writes:
>        Kahnung  : Ada.Streams.Stream_Element_Array := (1, 2, 3);
>        Last : Ada.Streams.Stream_Element_Offset;

the Last was missing.

After adding it, the code compiles and works.

Here is the working version (May be it helps someone who is searching
for a short, simple example too.):

-----
with GNAT.Sockets; use GNAT.Sockets;
with Ada.Command_Line; use Ada.Command_Line;
with Ada.Exceptions; use Ada.Exceptions;
with Ada.Streams; use Ada.Streams;

procedure myrdate is
    Address  : Sock_Addr_Type;
    Socket   : Socket_Type;
    Kahnung  : Ada.Streams.Stream_Element_Array := (1, 2, 3, 4);
    Last     : Ada.Streams.Stream_Element_Offset;

begin
    Initialize (Process_Blocking_IO => False);
    Address.Addr := Addresses (Get_Host_By_Name(Argument(1)), 1);
    Address.Port := 37;
    Create_Socket (Socket, Family_Inet, Socket_Datagram);
    Send_Socket (Socket, Kahnung, Last, Address);
    Receive_Socket (Socket, Kahnung, Last);
    Close_Socket(Socket);
    Finalize;
end myrdate;
-----

>    Send_Socket (Socket, Kahnung, Last, Address);
> ends up with a constraint error. Oh well, I guess I need to get GDB
> working now ...

In the original posted code there was some garbage left, which should
be removed, like the channel and RTime, ...


MvfG,

Arvids